staging: erofs: fix fast symlink w/o xattr when fs xattr is on

Currently, this will hit a BUG_ON for these symlinks as follows:

- kernel message
------------[ cut here ]------------
kernel BUG at drivers/staging/erofs/xattr.c:59!
SMP PTI
CPU: 1 PID: 1170 Comm: getllxattr Not tainted 4.20.0-rc6+ #92
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-2.fc27 04/01/2014
RIP: 0010:init_inode_xattrs+0x22b/0x270
Code: 48 0f 45 ea f0 ff 4d 34 74 0d 41 83 4c 24 e0 01 31 c0 e9 00 fe ff ff 48 89 ef e8 e0 31 9e ff eb e9 89 e8 e9 ef fd ff ff 0f 0$
 <0f> 0b 48 89 ef e8 fb f6 9c ff 48 8b 45 08 a8 01 75 24 f0 ff 4d 34
RSP: 0018:ffffa03ac026bdf8 EFLAGS: 00010246
------------[ cut here ]------------
...
Call Trace:
 erofs_listxattr+0x30/0x2c0
 ? selinux_inode_listxattr+0x5a/0x80
 ? kmem_cache_alloc+0x33/0x170
 ? security_inode_listxattr+0x27/0x40
 listxattr+0xaf/0xc0
 path_listxattr+0x5a/0xa0
 do_syscall_64+0x43/0xf0
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
...
---[ end trace 3c24b49408dc0c72 ]---

Fix it by checking ->xattr_isize in init_inode_xattrs(),
and it also fixes improper return value -ENOTSUPP
(it should be -ENODATA if xattr is enabled) for those inodes.

Fixes: b17500a0fdba ("staging: erofs: introduce xattr & acl support")
Cc: <stable@vger.kernel.org> # 4.19+
Reported-by: Li Guifu <bluce.liguifu@huawei.com>
Tested-by: Li Guifu <bluce.liguifu@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/erofs/inode.c b/drivers/staging/erofs/inode.c
index d7fbf5f4600f36c8d9d950aaafa2289d62abc59e..f99954dbfdb5878b2e76c820d18ec6a03f036674 100644 (file)
--- a/drivers/staging/erofs/inode.c
+++ b/drivers/staging/erofs/inode.c
@@ -185,16 +185,16 @@ static int fill_inode(struct inode *inode, int isdir)
                /* setup the new inode */
                if (S_ISREG(inode->i_mode)) {
 #ifdef CONFIG_EROFS_FS_XATTR
-                       if (vi->xattr_isize)
-                               inode->i_op = &erofs_generic_xattr_iops;
+                       inode->i_op = &erofs_generic_xattr_iops;
 #endif
                        inode->i_fop = &generic_ro_fops;
                } else if (S_ISDIR(inode->i_mode)) {
                        inode->i_op =
 #ifdef CONFIG_EROFS_FS_XATTR
-                               vi->xattr_isize ? &erofs_dir_xattr_iops :
-#endif
+                               &erofs_dir_xattr_iops;
+#else
                                &erofs_dir_iops;
+#endif
                        inode->i_fop = &erofs_dir_fops;
                } else if (S_ISLNK(inode->i_mode)) {
                        /* by default, page_get_link is used for symlink */

diff --git a/drivers/staging/erofs/xattr.c b/drivers/staging/erofs/xattr.c
index 59bc5641c4e7622042b379b7797ba5d2307d890b..1c9498e38f0e92b0c9891d0f0cb359c00435c1be 100644 (file)
--- a/drivers/staging/erofs/xattr.c
+++ b/drivers/staging/erofs/xattr.c
@@ -56,7 +56,26 @@ static int init_inode_xattrs(struct inode *inode)
                return 0;
 
        vi = EROFS_V(inode);
-       BUG_ON(!vi->xattr_isize);
+
+       /*
+        * bypass all xattr operations if ->xattr_isize is not greater than
+        * sizeof(struct erofs_xattr_ibody_header), in detail:
+        * 1) it is not enough to contain erofs_xattr_ibody_header then
+        *    ->xattr_isize should be 0 (it means no xattr);
+        * 2) it is just to contain erofs_xattr_ibody_header, which is on-disk
+        *    undefined right now (maybe use later with some new sb feature).
+        */
+       if (vi->xattr_isize == sizeof(struct erofs_xattr_ibody_header)) {
+               errln("xattr_isize %d of nid %llu is not supported yet",
+                     vi->xattr_isize, vi->nid);
+               return -ENOTSUPP;
+       } else if (vi->xattr_isize < sizeof(struct erofs_xattr_ibody_header)) {
+               if (unlikely(vi->xattr_isize)) {
+                       DBG_BUGON(1);
+                       return -EIO;    /* xattr ondisk layout error */
+               }
+               return -ENOATTR;
+       }
 
        sb = inode->i_sb;
        sbi = EROFS_SB(sb);
@@ -424,7 +443,6 @@ static int erofs_xattr_generic_get(const struct xattr_handler *handler,
                struct dentry *unused, struct inode *inode,
                const char *name, void *buffer, size_t size)
 {
-       struct erofs_vnode *const vi = EROFS_V(inode);
        struct erofs_sb_info *const sbi = EROFS_I_SB(inode);
 
        switch (handler->flags) {
@@ -442,9 +460,6 @@ static int erofs_xattr_generic_get(const struct xattr_handler *handler,
                return -EINVAL;
        }
 
-       if (!vi->xattr_isize)
-               return -ENOATTR;
-
        return erofs_getxattr(inode, handler->flags, name, buffer, size);
 }